Pronunciation: (pen'i-trunt), [key]
1. a person or thing that penetrates.
2. a compound that penetrates the skin, as a lotion or cream.
3. a substance that lowers the surface tension of water; wetting agent.
4. Zool.a large nematocyst discharging a barbed thread that penetrates the body of the prey and injects a toxic fluid.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.